The term “fluidised bed” is used to describe reactors with reaction zones where a fluid is passed through a bed of granular particles such that the granular particles move to some degree. The degree of solids movement leads to various categories of fluidised bed reactors including:                incipient (solids rolling but with little vertical or lateral movement)        bubbling or partial fluidised or slugging fluidised        fully fluidised        
Fluidised beds are typically used to transfer heat or mass between a fluid process stream and a solid process stream. For such applications, fluidised beds are very effective, however they are typically an expensive option due to the large cost of the equipment involved such as the requirement of large fans, complicated ducting underneath the bed, and complexity in design.
Fluidised beds are used for various applications including gas scrubbing, drying of solids, pyrolysis, gasification, calcining, catalytic reactions, catalysis cleaning and/or combustion of solids. Processes in which solids are contacted with a hot gas, such as drying, often result in decrepitation of the solids where they crack and break into smaller particles. Such decrepitation of the solids results in an excessive amount of fine particles being produced which are unable to be used and form a waste product.
Accordingly, the present invention seeks to provide a reactor for contacting a fluid with a solid that is relatively inexpensive compared to typical fluidised bed reactors whilst maintaining rates of heat and/or mass transfer. The present invention also seeks to provide a reactor for contacting a fluid with a solid that reduces any decrepitation of the solid being contacted with the fluid.